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A curve of constant width can rotate between two parallel lines separated by its width, while at all times touching those lines, which act as supporting lines for the rotated curve. In the same way, a curve of constant width can rotate within a rhombus or square, whose pairs of opposite sides are separated by the width and lie on parallel ...
The angles made by each pair of arcs at the corners of a Reuleaux triangle are all equal to 120°. This is the sharpest possible angle at any vertex of any curve of constant width. [9] Additionally, among the curves of constant width, the Reuleaux triangle is the one with both the largest and the smallest inscribed equilateral triangles. [15]
However, there are two different ways of smoothing subsets of the edges of the Reuleaux tetrahedron to form Meissner tetrahedra, surfaces of constant width. These shapes were conjectured by Bonnesen & Fenchel (1934) to have the minimum volume among all shapes with the same constant width, but this conjecture remains unsolved.
The same theorem is also true in the hyperbolic plane. [11] For any convex distance function on the plane (a distance defined as the norm of the vector difference of points, for any norm), an analogous theorem holds true, according to which the minimum-area curve of constant width is an intersection of three metric disks, each centered on a boundary point of the other two.
These Reuleaux polygons have constant width, and all have the same width; therefore by Barbier's theorem they also have equal perimeters. In geometry, Barbier's theorem states that every curve of constant width has perimeter π times its width, regardless of its precise shape. [1] This theorem was first published by Joseph-Émile Barbier in ...
More generally, if S is a surface of constant width w, then every projection of S is a curve of constant width, with the same width w. All curves of constant width have the same perimeter, the same value πw as the circumference of a circle with that width (this is Barbier's theorem). Therefore, every surface of constant width is also a surface ...
It can be used to characterize curves of constant width: a convex hedgehog has constant width if and only if its support function is formed by adding / to the support function of a projective hedgehog. That is, the curves of constant width are exactly the convex hedgehogs formed as sums of projective hedgehogs and circles.
Gambian dalasi coin, a Reuleaux heptagon. In geometry, a Reuleaux polygon is a curve of constant width made up of circular arcs of constant radius. [1] These shapes are named after their prototypical example, the Reuleaux triangle, which in turn is named after 19th-century German engineer Franz Reuleaux. [2]